Transition metal oxides have been a research hotspot for basic scientific research and frontier applications. Owing to the presence of d electrons and strong electron correlation, a wealth of physical phenomena emerges in the transition metal oxide family. In particular, extremely fruitful research progress is achieved in a 3d orbital elemental system. In comparison, the 4d transition metal oxides need more attention. Molybdate has excellent optical and electrical properties. Among AMoO ₃( A= Ca, Sr, Ba), only BaMoO ₃has not been reported for epitaxial films to date. In this work, high-quality epitaxial films of BaMoO ₃and BaMoO ₄are prepared by using the pulsed laser deposition. We conduct the oxygen partial pressure modulation experiments and the results show that the growth of BaMoO ₃is sensitive to oxygen partial pressure. Also, BaMoO ₃has a geometrically similar lattice structure to BaMoO ₄, and there exists epitaxial competition between BaMoO ₃and BaMoO ₄. These two points make the preparation of epitaxial BaMoO ₃films more challenging. The key to the preparation of epitaxial BaMoO ₃thin films is the reduced laser target material, high vacuum environment, and ultra-low oxygen partial pressure. The epitaxy competition can be avoided by using the SrTiO ₃(111) substrate. We conduct oxygen partial pressure modulation experiments on a narrow scale and reveal a self-assembled superlattice of epitaxial BaMoO ₃film on a SrTiO ₃(111) substrate. Both the satellite peaks in the XRD pattern and the HRTEM results indicate the superlattice period of about 7.04 Å. The oxygen partial pressure is the only parameter that regulates this phenomenon, so we presume that the essence of the self-assembled superlattice is periodic oxygen-induced lattice defects. Finally, electrical transport characterization experiments are conducted on representative BaMoO ₃films. The $\rho \text{-} T$ curve measurements and fitting results show that the epitaxial BaMoO ₃films on SrTiO ₃(001) substrates have better conductivities. The electrical transport properties of BaMoO ₃films grown on SrTiO ₃(111) substrates are dominated by electron-phonon scattering, and BaMoO ₃films grown on SrTiO ₃(001) substrate have stronger electron-electron scattering interactions. The resistivity of the self-assembled superlattice BaMoO ₃films is relatively high and electron-electron scattering plays an important role in determining the electrical transport property.